As is well known, reworking of a shaft for a gas turbine engine requires the removal of the outer coating on the shaft down to the parent metal and recoating the shaft to exactly its original dimension. Inherent in this process is that the entire surface of the shaft, at least at the bearing location, is coated; including the surface adjacent the lubrication holes in the shaft. It is necessary to obviate cracking problems that are susceptible in the coating in this vicinity that are occasioned when the shaft is operating. Thus, this localized coating must be removed without removal of the parent metal of the shaft prior to reassembling the shaft in the engine.
The heretofore method of this removal operation is to hand grind this area with a hand grinding tool. Obviously, the exactness of this technique was totally dependent on the skill of the operator of the grinder. Historically, this task was not only time consuming, but because of the exactness required, the incidence of rejecting the shafts because of poor grinds was high.
Another method heretofore used hand grind and chemically strip to remove the coating from the entire bearing journal (360.degree.). The area around the oil hole was then masked and the journal was recoated. This method, obviously, was expensive, time consuming and did not preclude leaking masks.